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Light is an important source to our brains. It often helps tell us what time of day it is and whether we should go to sleep or not based on this information. What would happen to our sleeping pattern if we had no indication if it was day or night? Would we still have a regular schedule? A French adventurer…
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Jetzt kostenlos anmeldenLight is an important source to our brains. It often helps tell us what time of day it is and whether we should go to sleep or not based on this information. What would happen to our sleeping pattern if we had no indication if it was day or night? Would we still have a regular schedule? A French adventurer and scientist, Michel Siffre, sought to find out.
Michel Siffre, a french adventurer, investigated how the absence of external cues could affect biological rhythms, namely, how a lack of light may interrupt his circadian rhythm. Siffre spent months in a cave without access to daylight and found his circadian rhythm was notably disrupted.
Fig. 1 - Michel Siffre explored how a lack of light affects our circadian rhythms.
We have a regular sleep/wake pattern on a 24-hour day due to biological rhythms – internal biological clocks in our body that govern different bodily functions/cycles. Siffre was interested in how a lack of external cues could disrupt our bodily rhythms, namely, the circadian rhythm.
The circadian rhythm lasts for 24 hours. A well-known circadian rhythm is a sleep-wake cycle. This cycle is our pattern of sleeping and wakefulness during a 24-hour day. Everyone's sleep-wake cycle is different, and different things can affect the sleep-wake cycle, such as external cues.
These external cues are called exogenous zeitgebers, and the most notable one affecting the sleep-wake cycle is daylight.
Biological rhythms
Internal biological clocks in our body govern different bodily functions/cycles.
Circadian rhythm
A biological rhythm that lasts for 24 hours. An example of a circadian rhythm is the sleep-wake cycle.
Siffre's cave study can be summarised in the following table. Here, we can see the timeline of what happened in the study and how Siffre attained his findings.
The aims of the study were to find out what it would be like for astronauts in space, where there were no exogenous zeitgebers such as daylight to affect our biological rhythms. Siffre wanted to find out what his natural sleep-wake cycle would be without any exogenous zeitgebers.
On 14 February 1972, Siffre went into Midnight Cave, Texas, USA and stayed there for six months. He stayed in a tent with a bed, table, and chair.
After some time in the cave, Siffre became depressed and despondent at his lack of freedom. He was also excruciatingly lonely, he wanted to trap a mouse so he would have some companionship, but in the process of trapping it, he accidentally killed the mouse. In his own words, 'Desolation overwhelms me.'
In addition, his record player broke, and his books got ruined due to dampness. His condition was so dire that Siffre thought of suicide. His short-term memory, mental health, and eyesight all got worse.
Here is an account of his experience in the cave:
Overcome with lethargy and bitterness, I sit on a rock and stare at my campsite in the bowels of Midnight Cave, near Del Rio, Texas. Behind me lie a hundred days of solitude; ahead loom two and a half more lonely months. But I - a wildly displaced Frenchman - know none of this, for I am living "beyond time," divorced from calendars and clocks and from sun and moon, to help determine, among other things, the natural rhythms of human life.—Siffre (1975)
For the first 35 days, Siffre had a sleep-wake cycle of 26 hours.
On day 37, he stayed up for a few more hours and then slept long. This pattern of being awake and then asleep for a long time occurred periodically for the next month.
Then on day 63, he returned to a cycle of 26 hours. Nine weeks later, his sleep-wake cycle became more varied and random again for 20 days.
Sometimes it was 48 hours as the people in previous studies. When his sleep-wake cycle varied, the cycle could be from 18–52 hours. On day 150, he returned to a 26-hour cycle that lasted until the experiment's end.
Fig. 3 - Michel Siffre spent six months in a cave to study the sleep-wake cycle.
Siffre thought astronauts could manage their biological rhythm without exogenous zeitgebers; however, they would need companionship as the isolation would not be manageable. Siffre concluded that time is not something humans could work with and understand without any external environmental cues.
Let's look at the strengths and weaknesses of Siffre's (1975) study.
First, let's explore the strengths of Siffre's cave study.
The study produced a lot of quantitative and qualitative data.
The study was done over a long time, six months, which allowed Siffre to investigate his sleep-wake cycle and show how irregular it became.
When Siffre woke up, strong lights were put on, and when he went to sleep, they were turned off. The lights could have acted as an external cue, which affects the study's internal validity.
Siffre was the only participant in the study, so it is hard to generalise his findings, such as how he did to astronauts.
Siffre lived in a cave alone for six months to investigate the sleep-wake cycle and what it would be like without any external environmental cues. In the cave, when Siffre woke up and thought it was daytime, he phoned the research team above ground, who switched on the lights in the cave. He conducted daily experiments, taking his blood pressure, memory, and physical tests. When he felt tired and thought it was nighttime, he would phone the research team again, they would turn the lights off, and Siffre would go to sleep.
Siffre conducted three experiments in total where he lived in a cave to investigate the sleep-wake cycle.
In Siffre (1975), he lived in a cave alone for six months. He was very lonely and became depressed, and his short-term memory, mental health and eyesight all got worse.
Although his sleep-wake cycle was irregular, it was manageable. In Siffre (1975), sometimes it was at a regular 26-hour cycle. When it varied, it could be anything between 18 and 52 hours. However, he thought time was not something humans could work with and understand without any external environmental cues.
Siffre proved that our internal body clock can still be managed without external environmental cues.
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